Method for controlling the engagement force of the synchronizers of a dual clutch transmission

Abstract

A method of controlling the engagement force of the synchronizers of a dual clutch transmission having a plurality of synchronizers to selectively engage and disengage various gear sets, and a plurality of shift actuators adapted to move the synchronizers. The method includes the steps of initiating a control routine to pressurize a shift actuator to move a synchronizer to a predetermined engagement position and determining the necessary level of force required to move the desired shift actuator to the predetermined engagement position such that the engagement movement is effected without excessive force. The method also includes the steps of determining the hydraulic pressure that corresponds to the determined level of force and varying the amount of available hydraulic line pressure delivered to the shift actuator such that the delivered pressure is the amount that corresponds to the determined level of force.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates, generally to the control of a dual clutch transmission and, more specifically, to a method for actively controlling the engagement force of the synchronizers of a dual clutch transmission for use in a motor vehicle driveline.[0003]2. Description of the Related Art[0004]Generally speaking, land vehicles require a powertrain consisting of three basic components. These components include a power plant (such as an internal combustion engine), a power transmission, and wheels. The power transmission component is typically referred to simply as the “transmission.” Engine torque and speed are converted in the transmission in accordance with the tractive-power demand of the vehicle. Presently, there are two typical transmissions widely available for use in conventional motor vehicles. The first, and oldest type is the manually operated transmission. These transmissions include a foot operated star...

AI Technical Summary

Benefits of technology

[0016]The disadvantages of the related art are overcome by the method of the present invention for controlling the engagement force of the synchronizers of a dual clutch transmission having a plurality of synchronizers to selectively engage and disengage various gear sets, and a plurality of shift actuators adapted to move the synchronizers. The method includes the steps of initiating a control routine to pressurize a shift actuator to move a synchronizer to a predetermined engagement position and determining the necessary level of force required to move the desired shift actuator to the predetermined engagement position such that the engagement movement is effected without excessive force. The method also includes the steps of determining the amount of hydraulic pressure that corresponds to the determined level of force and varying the amount of available hydraulic line pressure delivered to the shift actuator such that the delivered pressure is the amount that corresponds to the determined level of force. The method of the present invention determines the amount of force to apply to the shift actuators to move the synchronizer in response to various conditions and also how much continued force to apply as the synchronizer moves. The method of the present invention determines all the required force necessary to smoothly and efficiently move the synchronizer to its predetermined engagement position so that the engagement movement is effected without excessive force.

Problems solved by technology

One disadvantage of the manual transmission is that there is an interruption in the drive connection during gear shifting.

This results in losses in efficiency.

In addition, there is a great deal of physical interaction required on the part of the operator to shift gears in a vehicle that employs a manual transmission.

Although conventional automatic transmissions avoid an interruption in the drive connection during gear shifting, they suffer from the disadvantage of reduced efficiency because of the need for hydrokinetic devices, such as torque converters, interposed between the output of the engine and the input of the transmission for transferring kinetic energy therebetween.

In addition, automatic transmissions are typically more mechanically complex and therefore more expensive than manual transmissions.

Fluid couplings have inherent slip.

The inherent slip reduces the efficiency of the torque converter.

While torque converters provide a smooth coupling between the engine and the transmission, the slippage of the torque converter results in a parasitic loss, thereby decreasing the efficiency of the entire powertrain.

The power required to drive the pump and pressurize the fluid introduces additional parasitic losses of efficiency in the automatic transmission.

However, even with the inherent improvements of these newer automated transmissions, they still have the disadvantage of a power interruption in the drive connection between the input shaft and the output shaft during sequential gear shifting.

Power interrupted shifting results in a harsh shift feel that is generally considered to be unacceptable when compared to smooth shift feel associated with most conventional automatic transmissions.

While these power-shift dual clutch transmissions overcome several drawbacks associated with conventional transmissions and the newer automated manual transmissions, it has been found that controlling and regulating the automatically actuated dual clutch transmissions is a complicated matter and that the desired vehicle occupant comfort goals have not been achievable in the past.

Conventional control schemes and methods have generally failed to provide this capability.

However, they lack the ability to accurately determine the necessary force required to engage the synchronizers given the particular operating parameters present at the time of engagement to achieve smooth and efficient transmission operation.

If the shift engagement force is not properly calculated and executed, considering the operating parameters at the time, the shift will either be hard causing poor drivability and component wear, or the shift will be ineffectual and fail to engage the gear set.

Conventional dual clutch transmission control methods lack the ability to provide the proper shift engagement force.

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